ASIC (Application Specific Integrated Circuit) and custom logic typically are unforgiving systems since an error in the logic may not allow for an easy recovery once the device has been fabricated. The re-design cycle time can be 3-4 months. An FPGA (Field Programmable Gate Array), however, is an on the fly reconfigurable Boolean logic system. The heart of Reconfigurable logic is the configurable logic block which is formed using Boolean logic and can be altered very easily since an input digital signal can modify the operation of the logic block without physically altering it. The ability to program, use, reprogram, use and reprogram, use and continue this cycle infinitum are features very desirable which allow a system to adapt to different changing specifications or conditions quickly. The re-design cycle can be done in seconds. This helps explain why the reconfigurable logic business has grown into a several billion dollar enterprise.
Reconfigurable systems are very useful and allow for a rapid change to the system to achieve the desired behavior in a short time period. There are situations where some systems that would desire the ability to be reconfigurable but currently are not able to do so. These systems contain a component that is a discrete element: inductor, capacitor or antenna. It is difficult to replace these discrete elements with switches formed from active circuitry since the circuitry introduces loss and degrades the characteristics of the discrete elements. An RF (Radio Frequency) switch is used to switch the antenna from the transmitter to the receiver and the switch itself unfortunately introduces a loss of about 0.5 db. This is because it is difficult to replace metal with active components. In order to switch in a different value of an inductor, a first switch must disconnect the first inductor and a second switch must connect the new inductor. However, the switch introduces a loss and reduces the Q of the inductor; this is typically an undesirable effect. Finally, variable capacitors are currently formed by active devices; diodes or MOS gates, etc. These capacitors can behave nonlinearly and have a limited range of linear operation over a given voltage range.
In addition, wireless systems are comprised of hardware such as transmitters, receivers, DSPs (Digital Signal Processor), memory, D/A (Digital to Analog), A/D, filters and antennas. Typically, the wireless communication channel in a system may operate in a new frequency band. However, the system would perform better if the passive components could be changed to operate at that new frequency band. Since the hardware is physically soldered and bound in place in the system, it is very difficult to replace them with hardware that has been optimized to operate at this newer frequency band. One approach to this problem is to design the hardware so it operates over a larger frequency band. The consequences are a loss in gain and not being able to achieve the ultimate performance with an optimum design.
It would be very desirable to have a system that can be physically reconfigured to adapt to a changing conditions. For example, it would be desirable to have an inductor, antenna, capacitor or other hardware components to be physically alterable after they have been placed in the system. This specification addresses these concerns as described in the following section.